Influence of preparation conditions on the dispersion parameters of sprayed iron oxide thin films

Iron oxide thin films were prepared by spray pyrolysis technique (SPT) at various substrate temperatures (Tsub) and different deposition time. X-ray diffraction (XRD) analysis showed that, at Tsub ≥ 350 °C, a single phase of α-Fe2O3 film is formed which has the rhombohedral structure. Moreover, the crystallinity was improved by increasing Tsub. The effect of Tsub as well as deposition time on the optical dispersion of these films has been investigated. The optical transmittance and reflectance measurements were performed by using spectrophotometer in the wavelength range from 300 to 2500 nm. The refractive index was determined by using Murmann's exact equation. It was observed that, the refractive index increased with increasing in both the Tsub and film thickness. The optical dispersion parameters have been evaluated and analyzed by using Wemple-Didomenico equation. The obtained results showed that, the dielectric properties have weak dependencies of growth temperature and film thickness. At Tsub ≥ 350 °C, the average values of oscillator energy, Eo and dispersion energy, Ed were found to be 5.96 and 34.08 eV. While at different thickness, the average values of dispersion energies were found to be 3.93 and 17.08 eV. Also, the average values of oscillator strength So and single resonant frequency ωo were estimated 10.78 × 1013 m−2 and 5.99 × 1015 Hz, while at different thickness were evaluating 4.81 × 1013 m−2 and 6.11 × 1015 Hz. Furthermore, the optical parameters such as wavelength of single oscillator λo, plasma frequency ωp, and dielectric constant ɛ have been evaluated. The carrier concentration Nopt by using Drud's theory was obtained the range of 5.07 × 1025 m−3 to 1.04 × 1026 m−3.